Two important factors in GIS and mapping is geometry and topology. In GIS, geometry is used to define shape, location and spatial properties of different features. Thanks to geometry, one can calculate distances and areas, perform various types of analyses and much more. But a map does not have to be geometrically correct to serve its purpose. 

Topology describes the relationship between features and defines the spatial relations and connections. In certain maps, the topology is the main point. A famous example is the London tube map, created by Harry Beck in 1931. In this map, the geometry is distorted in favor of topology, in order to produce a map that is simple to read and displays the connectivity between stations. A simple example of how geometry and topology can look like, using the same data, is presented to the right.